Magnetoresistive (MR) and giant magnetoresistive (GMR) heads are uniquely susceptible to defects on the media that give rise to thermal asperities (TA), effects that suddenly heat or cool the read-head element. Such events shift and tilt the baseline of the magnetic readback signal, possibly scrambling the data. With fly heights falling below 1.2 μin, defects as small as 0.4 μin (and diameters less than 1 μm) can cause asperities.
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